Hard and soft tissue changes following alveolar ridge preservation: a systematic review

Objective: Two focused questions were addressed within this systematic review. Q1) What is the effect of alveolar ridge preservation on linear and volumetric alveolar site dimensions, keratinised measurements, histological characteristics and patient-based outcomes when compared to unassisted socket healing. Q2) What is the size effect of these outcomes in three different types of intervention (guided bone regeneration, socket grafting and socket seal). Materials and methods: An electronic search (MEDLINE, EMBASE, Cochrane Central Register LILACS, Web of Science) and hand-search was conducted up to June 2015. Randomised controlled trials (RCT) and controlled clinical trials (CCT); with unassisted socket healing as controls: were eligible in the analysis for Q1. RCTs, CCTs and large prospective case series with or without an unassisted socket healing as control group were eligible in the analysis for Q2. Results: Nine papers (8 RCTs and 1 CCTs) were included in the analysis for Q1 and 37 papers (29 RCTs, 7 CCTs and 1 case series) for Q2. The risk for bias was unclear or high in most of the studies. Q1: the standardised mean difference (SMD) in vertical mid-buccal bone height between ARP and a non-treated site was 0.739 mm (95% CI: 0.332 to 1.147). The SMD when proximal vertical bone height and horizontal bone width was compared was 0.796mm (95% CI: - 1.228 to 0.364) and 1.198 mm (95% CI: -0.0374 to 2.433). Examination of ARP sites revealed significant variation in vital and trabecular bone percentages and keratinised tissue width and thickness. Adverse events were routinely reported, with three papers reporting a high level of complications in the test and control groups and two papers reporting greater risks associated with ARP. No studies reported on variables associated with the patient experience in either the test or the control group. Q2: A pooled effect reduction (PER) in mid-buccal alveolar ridge height of -0.467 mm (95% CI: -0.866 to -0.069) was recorded for GBR procedures and -0.157 mm (95% CI: -0.554 to 0.239) for socket grafting. A proximal vertical bone height reduction of -0.356 mm (95% CI: -0.490 to -0.222) was recorded for GBR, with a horizontal dimensional reduction of -1.45 mm (95% CI: -1.892 to -1.008) measured following GBR and -1.613 mm (95% CI: -1.989 to -1.238) for socket grafting procedures. Five papers reported on histological findings after ARP. Two papers indicated an increase in the width of the keratinised tissue following GBR, with two papers reporting a reduction in the thickness of the keratinised tissue following GBR. Histological examination revealed extensive variations in the treatment protocols and biomaterials materials used to evaluate extraction socket healing. GBR studies reported a variation in total bone formation of 47.9 +/- 9.1% to 24.67 +/- 15.92%. Post-operative complications were reported by 29 papers, with the most common findings soft tissue inflammation and infection. Conclusion: ARP results in a significant reduction in the vertical bone dimensional change following tooth extraction when compared to unassisted socket healing. The reduction in horizontal alveolar bone dimensional change was found to be variable. No evidence was identified to clearly indicate the superior impact of a type of ARP intervention (GBR, socket filler and socket seal) on bone dimensional preservation, bone formation, keratinised tissue dimensions and patient complications.